BACKGROUND AIMS: We carried out a retrospective analysis of viability by diagnosis and dimethyl sulfoxide (DMSO) concentration in patients who had undergone autologous transplants using hematopoietic progenitor cells (HPC) after long-term storage (up to 17.8 years).METHODS: Viability was tested using flow cytometry for HPC that were harvested and preserved using a controlled rate freezer and 5% or 10% DMSO with human serum albumin, then stored in liquid nitrogen. Data from 262 samples were analyzed (249 myeloma patients and 13 other diagnoses): 100 consecutively thawed samples with a storage time of <1 year (all 10% DMSO), 50 consecutive samples stored for 1-4.9 years (10% DMSO), 50 samples stored for 5-9 years (5% DMSO) and all samples stored and used for transplant after >9 years (60 samples, 5% DMSO; two samples, 10% DMSO).RESULTS: No statistically significant difference in viability between the 5% DMSO and 10% DMSO groups was observed (P = 0.08), so the 1-4.9 years and 5-9 years were combined and the three groups (<1 year, 1-9 years and >9 years) were compared using an anova test. There was no difference in viability based on cryostorage period (P = 0.23) or between myeloma and other diagnoses (P = 0.45). No difference was seen in time to White blood cell (WBC) engraftment (P = 0.10) or to platelet engraftment between groups (P = 0.52).CONCLUSIONS: These data suggest that long-term storage in 5% DMSO and human serum albumin is safe.